Process for producing phosphorus-containing cyanohydrin esters

ABSTRACT

The present invention primarily relates to a process for producing certain phosphorus-containing cyanohydrin esters of formula (I) and the use thereof for producing glufosinate/glufosinate salts. The present invention further relates to a process for producing glufosinate/glufosinate salts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage entry of International ApplicationNo. PCT/EP2016/070301, filed 29 Aug. 2016, which claims priority toEuropean Patent Application No. 15183423.1, filed 2 Sep. 2015.

BACKGROUND Field

The present invention primarily relates to a process for producingcertain phosphorus-containing cyanohydrin esters of hereinbelow-definedformula (I) and the use thereof for producing glufosinate/glufosinatesalts. The present invention further relates to a process for producingglufosinate/glufosinate salts.

Description of Related Art

Phosphorus-containing cyanohydrin esters are valuable intermediates invarious industrial fields, in particular for producing biologicallyactive substances which can be employed in thepharmaceutical/agrochemical sector.

U.S. Pat. No. 4,168,963 describes a wide variety ofphosphorus-containing herbicidally active compounds, among which inparticular phosphinothricin(2-amino-4-[hydroxy(methyl)phosphinoyl]butanoic acid; common name:glufosinate, referred to hereinbelow as glufosinate) and the saltsthereof have attained commercial importance in the agrochemical sector.

Methods for producing intermediates for the synthesis of suchphosphorus-containing herbicidally active compounds, in particular ofglufosinate, are described in U.S. Pat. Nos. 4,521,348, 4,599,207 and6,359,162B1 for example.

Reactions of cyanohydrin esters and methanephosphonous esters aredescribed in U.S. Pat. No. 4,521,348 or 4,599,207 for example.

While the prior art processes for producing phosphorus-containingcyanohydrin esters allow production of the desired phosphorus-containingcyanohydrin esters, in some cases in very good yield, they do still havedisadvantages such as, for example, yields of phosphorus-containingcyanohydrin esters that are still in need of improvement, an excessivelyhigh proportion of coupling products or byproducts, excessively complexpurification/isolation of the phosphorus-containing cyanohydrin estersand/or reaction conditions that are excessively arduous in terms ofprocess/plant engineering.

SUMMARY

It is accordingly an object of the present invention to find a processfor producing phosphorus-containing cyanohydrin esters which providesthe phosphorus-containing cyanohydrin esters in further improved yieldand/or results in a lower proportion of coupling products or byproductsand in addition preferably allows for an improved reaction regime, forexample in terms of aspects relevant to safety, the environment and/orquality.

The hereinbelow-described process according to the invention achievesthis object.

The present invention provides a process for producingphosphorus-containing cyanohydrin esters of formula (I)

characterized in that a compound of formula (II)

is reacted with a compound of formula (III)

wherein in each case:

-   -   R¹ represents (C₁-C₁₂-alkyl, (C₁-C₁₂-haloalkyl, (C₆-C₁₀)-aryl,        (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,        (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl,    -   R² represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl, (C₆-C₁₀)-aryl,        (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,        (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl,    -   R³ and R⁴ each independently of one another represent hydrogen,        (C₁-C₄)-alkyl, phenyl or benzyl,    -   R⁵ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl, (C₆-C₁₀)-aryl,        (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,        (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl,    -   X represents oxygen or sulphur and    -   n is 0 or 1,

in the presence of one or more free-radical-forming substances (IV)wherein two separate metered streams (D1) and (D2) are metered into thereactor and these metered streams (D1) and (D2) have the followingcomposition:

metered stream (D1) comprises one or more compounds of formula (II) andone or more free-radical-forming substances (IV)

and

metered stream (D2) comprises one or more compounds of formula (III) andalso optionally one or more compounds of formula (II) and optionally oneor more free-radical-forming substances (IV),

wherein the reaction is carried out in continuous fashion.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The process according to the invention is carried out in a continuousmode of operation (i.e. a continuous process regime).

In the context of the present invention a continuous process regime isto be understood as meaning that compounds (i.e. reactants such ascompounds of formula (II) and (III)) are brought into the reactor(feeding/influx) while at the same time, but spatially removedtherefrom, compounds (i.e. products such as compounds of formula (I))are brought out of the reactor (discharging/efflux).

Such a continuous process regime is economically advantageous since, forexample, unproductive reactor times due to filling and emptyingprocesses and lengthened reaction times due to safety engineeringreasons, reactor-specific heat exchange performances and heating andcooling processes such as are encountered in semi-batch processes andbatch processes can be avoided/minimized.

In a discontinuous process regime by contrast, the steps of feeding ofreactants (i.e. of reactants such as compounds of formula (II) and(III)), reaction (i.e. reaction of the reactants) and discharging of theproducts (i.e. products such as compounds of formula (I)) from thereactor are effected consecutively or overlapping only in individualstages.

The process according to the invention, particularly in one of theembodiments of the process according to the invention described aspreferable/particularly preferable, affords the phosphorus-containingcyanohydrin esters of formula (I)/of hereinbelow-defined formulae(Ia)/(Ib) in improved yield and regularly in higher purity.

Overall, the processes according to the invention, and also the furtherhereinbelow-described process according to the invention for producingglufosinate, form fewer undesired secondary components so that theprocesses according to the invention are more efficient and moreenergy-saving.

In the process according to the invention at least a portion of thealtogether employed entirety of the free-radical-forming substances (IV)is mixed with at least a portion of the altogether employed entirety ofthe compounds of formula (II)/of hereinbelow-defined formula (IIa)before the resulting metered stream (D1) is metered into the reactor.

In the process according to the invention the metered streams (D1) and(D2) defined in the context of the present invention are metered intothe reactor (i.e. the reaction vessel) from separate (i.e. spatiallyremoved) receptacles.

The respective alkyl radicals of the radicals R¹, R², R³, R⁴ and R⁵ mayhave a straight-chain or branched-chain (branched) carbon skeleton.

The expression “(C₁-C₄)-alkyl” is a brief notation for an alkyl radicalhaving 1 to 4 carbon atoms, i.e. encompasses the radicals methyl, ethyl,1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methylpropyl or tert-butyl.General alkyl radicals having a larger specified range of carbon atoms,for example “(C₁-C₆)-alkyl”, correspondingly also encompassstraight-chain or branched alkyl radicals having a greater number ofcarbon atoms, i.e. in this example also the alkyl radicals having 5 and6 carbon atoms.

“Halogen” preferably refers to the group consisting of fluorine,chlorine, bromine and iodine. Haloalkyl, haloaryl, haloaralkyl andhalocycloalkyl respectively refer to alkyl, aryl, aralkyl and cycloalkylpartially or completely substituted by identical or different halogenatoms, preferably from the group fluorine, chlorine and bromine, inparticular from the group fluorine and chlorine. Thus haloalkylencompasses for example monohaloalkyl (=monohalogenalkyl), dihaloalkyl(=dihalogenalkyl), trihaloalkyl (=trihalogenalkyl) or else perhaloalkyl,for example CF₃8, CHF₂, CH₂F, CF₃CF₂, CH₂FCHCl, CCl₃, CHCl₂, CH₂CH₂Cl.The same applies for the other halogen-substituted radicals.

Suitable and preferred compounds of formula (II) include inter alia:methanephosphonous acid mono(C₁-C₆)-alkyl esters, monododecylmethanephosphonate, monophenyl methanephosphonate; ethanephosphonousacid mono(C₁-C₆)-alkyl esters, monododecyl ethanephosphonate, monophenylethanephosphonate; propanephosphonous acid mono(C₁-C₆)-alkyl esters,monododecyl propanephosphonate, monophenyl propanephosphonate;butanephosphonous acid mono(C₁-C₆)-alkyl esters, monododecylbutanephosphonate, monophenyl butanephosphonate; phenylphosphonous acidmono(C₁-C₆)-alkyl esters, monododecyl phenylphosphonate, monophenylphenylphosphonate; benzylphosphonous acid mono(C₁-C₆)-alkyl esters,monododecyl benzylphosphonate, monophenyl benzylphosphonate;methylthiophosphonous acid mono(C₁-C₆)-alkyl esters, monododecylmethylthiophosphonate, monophenyl methylthiophosphonate;dimethylphosphine oxide, diethylphosphine oxide, dipropylphosphineoxide, dibutylphosphine oxide, diphenylphosphine oxide,methylphenylphosphine oxide, dibenzylphosphine oxide, dimethylphosphinesulphide and diphenylphosphine sulphide.

The production of the compounds of formula (II) is known to thoseskilled in the art and may be effected according to processes known fromthe literature (for example U.S. Pat. Nos. 3,914,345; 4,474,711;4,485,052; 4,839,105; 5,128,495).

The production of the cyanohydrin esters of formula (III) is likewiseknown to those skilled in the art and may be effected according toprocesses known from the literature (for example as per EP 0 019 750 A1and as per U.S. Pat. No. 4,521,348 and the relevant documents citedtherein).

It is preferable when in the process according to the invention:

R³ and R⁴ each independently of one another represent hydrogen ormethyl,

and/or

X represents oxygen,

and/or

n is 1.

The process according to the invention preferably relates to theproduction of phosphorus-containing cyanohydrin esters of formula (Ia)

characterized in that a compound of formula (IIa)

is reacted with an acrolein cyanohydrin ester of formula (IIIa), whereinone of the compounds or the compound of formula (III) corresponds toformula (IIIa) (acrolein cyanohydrin-O-acetate, Ac=acetyl, R⁵ in formula(I) correspondingly=methyl)

wherein in each case:

-   -   R¹ represents (C₁-C₆)-alkyl, (C₁-C₆)-haloalkyl, (C₆-C₈)-aryl,        (C₆-C₈)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,        (C₅-C₈)-cycloalkyl or (C₅-C₈)-halocycloalkyl and    -   R² represents (C₁-C₆)-alkyl, (C₁-C₆)-haloalkyl, (C₆-C₈)-aryl,        (C₆-C₈)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,        (C₅-C₈)-cycloalkyl or (C₅-C₈)-halocycloalkyl.

It is preferable when in each case:

-   -   R¹ represents (C₁-C₄)-alkyl or (C₁-C₄)-haloalkyl, preferably        methyl or ethyl,    -   R² represents (C₁-C₆)-alkyl or (C₁-C₆)-haloalkyl, preferably        (C₃-C₆)-alkyl, preference among these in turn being given to        C₄-alkyl or C₅-alkyl.

In the process according to the invention, in formula (I)/in formula(Ia)

R¹ particularly preferably represents methyl and

R² particularly preferably represents (C₁-C₆)-alkyl, preference in turnbeing given to (C₄-C₅)-alkyl.

Furthermore, in the process according to the invention preferably atleast a portion of the altogether employed entirety of the compounds offormula (II)/(IIa) is mixed with the compound(s) of formula (III)/(IIIa)and optionally in addition with one or more free-radical-formingsubstances (IV) before the resulting metered stream (D2) is metered intothe reactor.

The implementations which follow and the embodiments of the processaccording to the invention characterized as preferable/particularlypreferable apply in particular for the reaction of a compound of formula(IIa), in which R¹ represents methyl (and thus corresponds to thehereinbelow-defined compound of formula (IIb)) and R² represents(C₁-C₆)-alkyl, with the acrolein cyanohydrin esters of formula (IIIa).

A preferred process according to the invention is characterized in that

metered stream (D1) comprises one or more compounds of formula (II) andone or more free-radical-forming substances (IV), wherein metered stream(D1) comprises 10-100 mol % of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in thereaction.

A preferred process according to the invention is characterized in that

metered stream (D1) comprises 20-100 mol % of the entirety of the amountof the free-radical-forming substances (IV) altogether employed in thereaction, by preference 25-100 mol %, preferably 30-100 mol %.

A more preferred process according to the invention is characterized inthat

metered stream (D1) comprises 40-100 mol % of the entirety of the amountof the free-radical-forming substances (IV) altogether employed in thereaction, by preference 50-100 mol %, preferably 60-100 mol %, morepreferably 70-100 mol %, yet more preferably 80-100 mol %, particularlypreferably 90-100 mol %, especially preferably 95-100 mol %.

A more preferred process according to the invention is characterized inthat

metered stream (D1) comprises 80-100 wt %, preferably 90-100 wt %,preferably 95-100 wt %, especially preferably 100 wt %, of the entiretyof the amount of compounds of formula (II) altogether employed in themetered streams (D1) and (D2).

An alternative preferred embodiment of the process according to theinvention is characterized in that metered stream (D1) comprises 10-90wt %, preferably 20-80 wt %, more preferably 25-75 wt %, particularlypreferably 30-70 wt % and especially preferably 40-60 wt % of theentirety of the amount of compounds of formula (II) altogether employedin the metered streams (D1) and (D2).

A preferred process according to the invention is characterized in that

metered stream (D2) comprises 80-100 wt %, preferably 90-100 wt %,preferably 95-100 wt %, especially preferably 100 wt %, of the entiretyof the amount of compounds of formula (III) altogether employed in themetered streams (D1) and (D2).

A particularly preferred process according to the invention ischaracterized in that

metered stream (D1) comprises 40-100 mol %, by preference 50-100 mol %,preferably 60-100 mol %, more preferably 70-100 mol %, especiallypreferably 80-100 mol % and particularly preferably 90-100 mol % of theentirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2);

and/or

metered stream (D2) comprises 0-60 mol %, by preference 0-50 mol %,preferably 0-40 mol %, more preferably 0-30 mol %, especially preferably0-20 mol % and particularly preferably 0-10 mol % of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2).

In a particularly preferred embodiment the process according to theinvention is characterized in that metered stream (D1) comprises 90-100mol %, by preference 95-100 mol %, preferably 97-100 mol %, morepreferably 98-100 mol %, of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in the meteredstreams (D1) and (D2)

and metered stream (D2) comprises 0-10 mol %, by preference 0-5 mol %,preferably 0-3 mol %, more preferably 0-2 mol %, of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2).

In a particularly preferred embodiment the process according to theinvention is characterized in that metered stream (D1) comprises 99-100mol %, preferably 100 mol %, of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in the meteredstreams (D1) and (D2)

and

metered stream (D2) comprises 0-1 mol %, preferably 0 mol %, of theentirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2).

A particularly preferred process according to the invention ischaracterized in that the entirety of the compounds (II) and (IV) in themetered stream (D1) is 75 to 100 wt %, preferably 80 to 100 wt %, morepreferably 85 to 100 wt %, particularly preferably 90 to 100 wt %, ineach case based on the total weight of the metered stream (D1).

The process according to the invention is preferably carried out suchthat the metered streams (D1) and (D2) are metered into the reactorpredominantly simultaneously, preferably simultaneously.

The process according to the invention is preferably carried out underconditions in which free-radicals are formed.

The reaction of the compounds of formula (II) and (III)/of formula (IIa)and (IIIa) to afford the compounds of formula (I)/(Ia) in a processaccording to the invention is preferably effected with the aid of afree-radical-forming source, for example using electromagnetic fieldssuch as UV radiation, gamma radiation or X-rays, electric fields orelectrochemical methods or in the presence of one or morefree-radical-forming substances.

In the context of the process according to the invention it ispreferable to employ free-radical-forming substances.

A preferred process according to the invention is characterized in thatone, more than one or all of the free-radical-forming substances (IV)conform to formula (V)

wherein

-   -   R⁶ independently at each occurrence represents hydrogen,        (C₁-C₁₀)-alkyl, by preference (C₁-C₆)-alkyl, preferably        (C₁-C₄)-alkyl,    -   R⁷ represents hydrogen or (C₁-C₁₀)-alkyl, by preference hydrogen        or (C₁-C₆)-alkyl, preferably hydrogen or (C₁-C₄)-alkyl,

and

R⁸ represents methyl, ethyl, 2,2-dimethylpropyl or phenyl.

Preferred free-radical-forming substances of formula (V) are those inwhich

R⁶ independently at each occurence represents (C₁-C₁₀)-alkyl, bypreference (C₁-C₆)-alkyl, preferably (C₁-C₄)-alkyl,

R⁷ represents hydrogen or (C₁-C₁₀)-alkyl, by preference hydrogen or(C₁-C₆)-alkyl, preferably hydrogen or (C₁-C₄)-alkyl,

and

R⁸ represents methyl, ethyl, 2,2-dimethylpropyl or phenyl.

The free-radical-formers (radical initiators) of formula (V) are knownper se and in some cases commercially available.

The free-radical-formers of formula (V) in this context are preferablyselected from the group consisting of tert-butyl peroxypivalate,tert-amyl peroxypivalate, tert-butyl peroxyneodecanoate,1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, cumylperoxyneodecanoate, cumyl peroxyneoheptanoate, cumyl peroxypivalate andmixtures thereof.

The free-radical-formers of formula (V) in this context are preferablyselected from the group consisting of tert-butyl peroxyneodecanoate,1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, cumyl peroxyneodecanoate and mixtures thereof,particular preference in turn being given to 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxyneodecanoate and/or tert-butylperoxy-2-ethylhexanoate.

The process according to the invention allows production of thephosphorus-containing cyanohydrin esters of formula (I) or (Ia)/ofhereinbelow-defined formula (Ib) under mild reaction conditions and in amanner that is simpler to carry out in terms of process/plantengineering. The phosphorus-containing cyanohydrin esters of formula(I), (Ia) and (Ib) can therefore be obtained more easily in processengineering terms, in even better yields and in high purity.

The process according to the invention is preferably carried out suchthat the reaction is effected at a temperature in the range from 40° C.to 120° C., preferably at a temperature in the range from 50° C. to 110°C., more preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Performing the process according to the invention thus significantlyreduces or largely avoids a disproportionation of reactants of formula(II)/(IIa) for example. Performing the process according to theinvention also significantly reduces or largely avoids theoligomerization and polymerization of the compounds of formula(III)/(IIIa).

It is advantageous in the context of the process according to theinvention to employ the cyanohydrin esters of formula (III)/(IIIa) inthe highest possible purity. It is preferable when the cyanohydrinesters of formula (III)/(IIIa) are employed in a purity of not less than90 wt %, preferably of not less than 92 wt %, more preferably of notless than 95 wt %, especially preferably of not less than 98 wt %.

The formed phosphorus-containing cyanohydrin esters of formula(I)/(Ia)/hereinbelow-defined formula (Ib) may be used as startingmaterials for the synthesis of phosphorus-containing amino acids, forexample glufosinate (such a synthesis route is more particularlydescribed hereinbelow).

To avoid undesired side reactions and thus to achieve high yields it isadditionally advantageous to employ the phosphorus-containing reactant(II)/(IIa) in a molar excess based on the cyanohydrin esters of formula(III)/(IIIa).

The process according to the invention in these preferred embodimentsfurther has the advantage that no large excesses of compounds of formula(II)/(IIa) based on the employed entirety of compounds of formula(III)/(IIIa) are required to achieve the advantageous effects of theprocess according to the invention.

Preferably, in the process according to the invention the molar ratio ofthe entirety of the employed compound of formula (II)/(IIa) to theentirety of the employed compound of formula (III)/(IIIa) is in therange from 8:1 to 1:1, preferably in the range from 5:1 to 2:1.

Preferably, in the process according to the invention the molar ratio ofthe entirety of the employed compound of formula (II)/(IIa) to theentirety of the employed compound of formula (III)/(IIIa) is in therange from 5:1 to 5:2, more preferably in the range from 9:2 to 5:2.

Particularly preferred embodiments of the process according to theinvention for producing the compounds of formula (I) by reaction of acompound of formula (II) with the acrolein cyanohydrin ester of formula(III) are characterized in that

metered stream (D1) comprises 30-100 mol % of the entirety of the amountof the free-radical-forming substances (IV) altogether employed in thereaction, by preference 40-100 mol %, preferably 50-100 mol %, morepreferably 60-100 mol %, yet more preferably 70-100 mol %, particularlypreferably 80-100 mol %, especially preferably 90-100 mol % and mostpreferably 95-100 mol %, the entirety of the compounds (II) and (IV) inthe metered stream (D1) is 75 to 100 wt %, preferably 80 to 100 wt %,more preferably 85 to 100 wt %, particularly preferably 90 to 100 wt %,in each case based on the total weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula (II)to the entirety of the employed compound of formula (III) is in therange from 8:1 to 1:1, preferably in the range from 5:1 to 2:1

and

the reaction is effected at a temperature in the range from 40° C. to120° C., preferably at a temperature in the range from 50° C. to 110°C., more preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Particularly preferred embodiments of the process according to theinvention for producing the compounds of formula (I) by reaction of acompound of formula (II) with the acrolein cyanohydrin ester of formula(III) are characterized in that

metered stream (D1) comprises 40-100 mol %, by preference 50-100 mol %,preferably 60-100 mol %, more preferably 70-100 mol %, especiallypreferably 80-100 mol % and particularly preferably 90-100 mol % of theentirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2),

metered stream (D2) comprises 0-60 mol %, by preference 0-50 mol %,preferably 0-40 mol %, more preferably 0-30 mol %, especially preferably0-20 mol % and particularly preferably 0-10 mol % of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2),

the entirety of the compounds (II) and (IV) in the metered stream (D1)is 75 to 100 wt %, preferably 80 to 100 wt %, more preferably 85 to 100wt %, particularly preferably 90 to 100 wt %, in each case based on thetotal weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula (II)to the entirety of the employed compound of formula (III) is in therange from 8:1 to 1:1, preferably in the range from 5:1 to 2:1, whereinone, more than one or all of the free-radical-forming substances (IV)conform to formula (V) and are preferably selected from the groupconsisting of tert-butyl peroxypivalate, tert-amyl peroxypivalate,tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amylperoxyneodecanoate, cumyl peroxyneodecanoate, cumyl peroxyneoheptanoate,cumyl peroxypivalate and mixtures thereof

and

the reaction is effected at a temperature in the range from 40° C. to120° C., preferably at a temperature in the range from 50° C. to 110°C., more preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Particularly preferred embodiments of the process according to theinvention for producing the compounds of formula (I) by reaction of acompound of formula (II) with the acrolein cyanohydrin ester of formula(III), in particular for producing the compounds of formula (Ia) byreaction of a compound of formula (IIa) with the acrolein cyanohydrinester of formula (IIIa) are characterized in that

metered stream (D1) comprises 50-100 mol %, preferably 60-100 mol %,more preferably 70-100 mol %, especially preferably 80-100 mol % andparticularly preferably 90-100 mol % of the entirety of the amount ofthe free-radical-forming substances (IV) altogether employed in themetered streams (D1) and (D2),

metered stream (D2) comprises 0-50 mol %, preferably 0-40 mol %, morepreferably 0-30 mol %, especially preferably 0-20 mol % and particularlypreferably 0-10 mol % of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in the meteredstreams (D1) and (D2),

the entirety of the compounds (II)/(IIa) and (IV) in the metered stream(D1) is 80 to 100 wt %, preferably 85 to 100 wt %, particularlypreferably 90 to 100 wt %, in each case based on the total weight of themetered stream (D1),

the molar ratio of the entirety of the employed compound of formula(II)/(IIa) to the entirety of the employed compound of formula(III)/(IIIa) is in the range from 5:1 to 2:1,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are preferably selected from the groupconsisting of tert-butyl peroxypivalate, tert-amyl peroxypivalate,tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amylperoxyneodecanoate, cumyl peroxyneodecanoate, cumyl peroxyneoheptanoate,cumyl peroxypivalate and mixtures thereof

and

the reaction is effected at a temperature in the range from 50° C. to110° C., preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Particularly preferred embodiments of the process according to theinvention for producing the compounds of formula (I) by reaction of acompound of formula (II) with the acrolein cyanohydrin ester of formula(III), in particular for producing the compounds of formula (Ia) byreaction of a compound of formula (IIa) with the acrolein cyanohydrinester of formula (IIIa) are characterized in that

metered stream (D1) comprises 70-100 mol %, especially preferably 80-100mol % and particularly preferably 90-100 mol % of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streamss (D1) and (D2),

metered stream (D2) comprises 0-30 mol %, especially preferably 0-20 mol% and particularly preferably 0-10 mol % of the entirety of the amountof the free-radical-forming substances (IV) altogether employed in themetered streamss (D1) and (D2),

the entirety of the compounds (II)/(IIa) and (IV) in the metered stream(D1) is 80 to 100 wt %, preferably 85 to 100 wt %, particularlypreferably 90 to 100 wt %, in each case based on the total weight of themetered stream (D1),

the molar ratio of the entirety of the employed compound of formula(II)/(IIa) to the entirety of the employed compound of formula(III)/(IIIa) is in the range from 5:1 to 2:1,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are selected from the group consistingof tert-butyl peroxypivalate, tert-amyl peroxypivalate, tert-butylperoxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate,tert-butyl peroxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, cumylperoxyneodecanoate, cumyl peroxyneoheptanoate, cumyl peroxypivalate andmixtures thereof

and

the reaction is effected at a temperature in the range from 50° C. to110° C., preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa) with the acrolein cyanohydrin ester of formula(IIIa) are characterized in that

metered stream (D1) comprises 70-100 mol %, especially preferably 80-100mol % and particularly preferably 90-100 mol % of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2),

metered stream (D2) comprises 0-30 mol %, especially preferably 0-20 mol% and particularly preferably 0-10 mol % of the entirety of the amountof the free-radical-forming substances (IV) altogether employed in themetered streams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 80 to 100 wt %, preferably 85 to 100 wt %, particularly preferably 90to 100 wt %, in each case based on the total weight of the meteredstream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 5:1 to 2:1,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are selected from the group consistingof tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, cumylperoxyneodecanoate and mixtures thereof, particular preference in turnbeing given to 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate and/or tert-butyl peroxy-2-ethylhexanoate

and

the reaction is effected at a temperature in the range from 50° C. to110° C., preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa) with the acrolein cyanohydrin ester of formula(IIIa) are characterized in that

metered stream (D1) comprises 80-100 mol %, preferably 90-100 mol %, ofthe entirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2),

metered stream (D2) comprises 0-20 mol %, preferably 0-10 mol %, of theentirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 85 to 100 wt %, preferably 90 to 100 wt %, in each case based on thetotal weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 5:1 to 5:2,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are selected from the group consistingof tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, cumylperoxyneodecanoate and mixtures thereof, particular preference in turnbeing given to 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate and/or tert-butyl peroxy-2-ethylhexanoate

and

the reaction is effected at a temperature in the range from 50° C. to110° C., preferably at a temperature in the range from 55° C. to 100° C.and particularly preferably at a temperature in the range from 60° C. to95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa), in which R¹ represents methyl (and thuscorresponds to the hereinbelow-defined compound of formula (IIb)) and R²represents (C₁-C₆)-alkyl, with the acrolein cyanohydrin esters offormula (IIIa) are characterized in that

metered stream (D1) comprises 90-100 mol %, by preference 95-100 mol %,preferably 97-100 mol %, more preferably 98-100 mol %, of the entiretyof the amount of the free-radical-forming substances (IV) altogetheremployed in the metered streams (D1) and (D2),

metered stream (D2) comprises 0-10 mol %, by preference 0-5 mol %,preferably 0-3 mol %, more preferably 0-2 mol %, of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 85 to 100 wt %, preferably 90 to 100 wt %, in each case based on thetotal weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 5:1 to 5:2,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are selected from the group consistingof tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, cumylperoxyneodecanoate and mixtures thereof, particular preference in turnbeing given to 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate and/or tert-butyl peroxy-2-ethylhexanoate

and

the reaction is effected at a temperature in the range from 55° C. to100° C., particularly preferably at a temperature in the range from 60°C. to 95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa), in which R¹ represents methyl (and thuscorresponds to the hereinbelow-defined compound of formula (IIb)) and R²represents (C₁-C₆)-alkyl, with the acrolein cyanohydrin esters offormula (IIIa) are characterized in that

metered stream (D1) comprises 90-100 mol %, by preference 95-100 mol %,preferably 97-100 mol %, more preferably 98-100 mol %, of the entiretyof the amount of the free-radical-forming substances (IV) altogetheremployed in the metered streams (D1) and (D2),

metered stream (D2) comprises 0-10 mol %, by preference 0-5 mol %,preferably 0-3 mol %, more preferably 0-2 mol %, of the entirety of theamount of the free-radical-forming substances (IV) altogether employedin the metered streams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 85 to 100 wt %, preferably 90 to 100 wt %, in each case based on thetotal weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 9:2 to 5:2,

wherein one, more than one or all of the free-radical-forming substances(IV) conform to formula (V) and are selected from the group consistingof tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate,1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, cumylperoxyneodecanoate and mixtures thereof, particular preference in turnbeing given to 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate and/or tert-butyl peroxy-2-ethylhexanoate

and

the reaction is effected at a temperature in the range from 55° C. to100° C., particularly preferably at a temperature in the range from 60°C. to 95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa), in which R¹ represents methyl (and thuscorresponds to the hereinbelow-defined compound of formula (IIb)) and R²represents (C₁-C₆)-alkyl, with the acrolein cyanohydrin ester of formula(IIIa) are characterized in that

metered stream (D1) comprises 95-100 mol %, preferably 97-100 mol %,more preferably 98-100 mol % of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in the meteredstreams (D1) and (D2),

metered stream (D2) comprises 0-5 mol %, preferably 0-3 mol %, morepreferably 0-2 mol % of the entirety of the amount of thefree-radical-forming substances (IV) altogether employed in the meteredstreams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 90 to 100 wt % based on the total weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 9:2 to 5:2,

wherein all of the free-radical-forming substances (IV) conform toformula (V) and are selected from the group consisting of1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate and mixturesthereof

and

the reaction is effected at a temperature in the range from 55° C. to100° C., particularly preferably at a temperature in the range from 60°C. to 95° C.

Especially preferred embodiments of the process according to theinvention for producing the compounds of formula (Ia) by reaction of acompound of formula (IIa), in which R¹ represents methyl (and thuscorresponds to the hereinbelow-defined compound of formula (IIb)) and R²represents (C₁-C₆)-alkyl, with the acrolein cyanohydrin ester of formula(IIIa) are characterized in that

metered stream (D1) comprises 97-100 mol %, preferably 98-100 mol %, ofthe entirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2),

metered stream (D2) comprises 0-3 mol %, preferably 0-2 mol %, of theentirety of the amount of the free-radical-forming substances (IV)altogether employed in the metered streams (D1) and (D2),

the entirety of the compounds (IIa) and (IV) in the metered stream (D1)is 90 to 100 wt % based on the total weight of the metered stream (D1),

the molar ratio of the entirety of the employed compound of formula(IIa) to the entirety of the employed compound of formula (IIIa) is inthe range from 9:2 to 5:2,

wherein all of the free-radical-forming substances (IV) conform toformula (V) and are selected from the group consisting of1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxyneodecanoate, tert-butyl peroxy-2-ethylhexanoate and mixturesthereof

and

the reaction is effected at a temperature in the range from 60° C. to95° C.

The process according to the invention is preferably carried out underinertization, preferably in a protective gas atmosphere. Preferredprotective gases are nitrogen/argon.

It is further possible to carry out the process according to theinvention under superatmospheric pressure or under reduced pressure.

The process according to the invention may be carried out in an optionaldiluent.

Usable optional diluents in principle include various organic solvents,preferably toluene, xylene, chlorobenzene, dichlorobenzene, dimethylformamide (DMF), dimethylacetamide, N-methyl-2-pyrrolidone (NMP) ormixtures of these organic solvents. The process according to theinvention is preferably carried out without such further optionalsolvents.

However, it may be advantageous to carry out the process according tothe invention in previously formed reaction product of formula (I), (Ia)or (Ib) as diluent.

In a continuous mode of operation in particular it is advantageous tocarry out the process according to the invention in previously formedreaction product of formula (I), (Ia) or (Ib) or in a mixture ofreaction product of formula (I), (Ia) or (Ib) and reactant of formula(II)/(IIa) as diluent.

The purity of the desired products of formula (I) after purification,for example after distillative removal of an excess of the component(II)/(IIa), is regularly greater than 95%. A preferably recovered excessof the starting compound (II)/(IIa) may subsequently be reemployed inthe same reaction without further purification.

This applies in particular for the compound of formula (Ib) whereR²=n-butyl which is obtained by the process according to the inventionby reaction of the phosphorus-containing reactant (IIa) where R¹=methyland R²=n-butyl with acrolein cyanohydrin-O-acetate of formula (IIIa).

Glufosinate salts in the context of the present invention are preferablyammonium salts, phosphonium salts, sulphonium salts, alkali metal saltsand alkaline earth metal salts of glufosinate.

Especially preferred in the context of the present invention areglufosinate, glufosinate sodium and glufosinate ammonium.

In a further aspect the present invention relates to the production ofglufosinate

or glufosinate salts (preferably glufosinate ammonium) characterized inthat in this process a compound of formula (Ib) is employed

wherein R² has the meaning defined in accordance with the inventionhereinabove, preferably the meaning defined as preferable hereinaboveand particularly preferably the meaning defined as particularlypreferable hereinabove and

R⁵ has the meaning recited hereinabove and preferably represents methyland

the production of the compound of formula (Ib) is effected by a processdefined in accordance with the invention.

In a preferred aspect the present invention relates to the production ofglufosinate and/or glufosinate salts

characterized by reaction of a compound of formula (Ib) by the followingstep:

reaction of a compound of formula (IIb)

wherein

R² represents (C₁-C₆)-alkyl, preferably (C₄-C₅)-alkyl and particularlypreferably n-butyl or n-pentyl,

with acrolein cyanohydrin-O-acetate of formula (IIIA)

wherein the reaction of (IIb) with (IIIa) is effected by thehereinabove-described process according to the invention, preferably inone of the embodiments described as preferable and particularlypreferably in one of the embodiments described as particularlypreferable.

The process according to the invention for producing glufosinate and/orglufosinate salts is further preferably effected by reaction of acompound of formula (Ib) with NH₃ to afford compound (VI),

wherein R² and R⁵ each have the meaning recited hereinabove,

and subsequent hydrolysis of compound (VI) to afford glufosinate/thesalts thereof.

The process according to the invention for producing glufosinate and/orglufosinate salts may be effected in similar fashion as described forexample in U.S. Pat. No. 4,521,348.

Finally, the present invention also relates to the use of a compound offormula (I)/(Ib) as defined hereinabove and produced by a processaccording to the invention for producing glufosinate/glufosinate salts,in particular glufosinate, glufosinate sodium or glufosinate ammonium.

The present invention further relates to a process for producingglufosinate/glufosinate salts, in particular glufosinate, glufosinatesodium or glufosinate ammonium, comprising the following steps (a) and(b):

(a) producing of a compound of formula (I)/(Ib) as defined hereinabove,

(b) use of the compound of formula (I)/(Ib) obtained in step (a) forproducing glufosinate/glufosinate salts, in particular glufosinate,glufosinate sodium or glufosinate ammonium.

The examples which follow elucidate the present invention.

EXAMPLES

All data are based on weight unless otherwise stated.

Abbreviations used:

MPE: methanephosphonous acid mono-n-butyl ester

ACA: acrolein cyanohydrin acetate

ACM: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate

Example 1 n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

Discontinuous Mode of Operation

A temperature-controllable, cylindrical glass reactor was filled with aportion of the required MPE to adequately cover the stirring means andthe reactor contents were brought to reaction temperature (typically 85°C.). In the experiments with a pumped circulation system/circulationloop, the circulation loop including the associated pump was also filledwith MPE. Commixing of the reactor contents was accomplished via asix-blade disc stirrer in combination with four baffles. The reactorcontents were always blanketed with nitrogen and the reactor wasoperated without application of superatmospheric pressure.

To ensure reliable starting of the reaction (i.e. reliable initiation),5 minutes before commencement of the metering of the reactants into thereactor a small amount of initiator (0.9-1.0 mL, corresponding to about0.8-0.9 g) was injected into the initially charged MPE previously heatedto reaction temperature (and possibly also circulating through thecirculation loop). The time interval of 5 minutes correspondsapproximately to the half-life of the free-radical initiator tert-butylperneodecanoate at 85° C. Toward the end of the metering time of 4 hours(i.e. more than 40 half-lives of the employed free-radical initiator)the initially injected amount of tert-butyl perneodecanoate had fallento <10⁻¹³ parts of the starting amount and thus had no appreciablefurther relevance for the ACM production in the continuous mode ofoperation according to hereinbelow-reported example 2.

The reactants E1 and E2 were then separately metered into the reactoruntil the desired fill-level had been achieved, taking into account therespective stoichiometries.

142.0 g of MPE (98% purity) were initially charged and heated to 85° C.5 min before commencement of the metering of the reactants E1 and E2,1.0 ml (about 0.9 g) of the free-radical initiator tert-butylperneodecanoate (98% purity) was added. The following reactants E1 andE2 were then simultaneously metered into the reactor over a period of4.0 h:

reactants E1 was a mixture of MPE (102.1 g, 98% purity) and tert-butylperneodecanoate (3.0 g, 98% purity), reactant E2 was composed of 57.0 gof ACA (99% purity).

The concentration of the free-radical initiator was accordingly 1.0 wt %based on the overall mixture.

After expiry of the metering time the discontinuous batch had reachedits endpoint; the employed ACA had reacted completely.

Example 2 n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

Continuous Mode of Operation

The reactor was initially charged with a mixture produced by thediscontinuous mode of operation according to hereinabove-reportedexample 1. The reaction conditions and the apparatus parameters were thesame as those from example 1. At a reaction temperature of 85° C., themetered streams (D1) and (D2) were then simultaneously and separatelymetered into the reactor.

At 85° C., metered stream (D1), a mixture of MPE and free-radicalinitiator tert-butyl perneodecanoate, was added to the reactor at 63mL/h and metered stream (D2), ACA, was added to the reactor at 14 mL/h,the content of the free-radical initiator in the MPE (1.2 wt %) beingchosen such that a content of 1.0 wt % of free-radical initiator in theoverall mixture in the reactor was achieved.

Corresponding to the supplied volume flows, an adequately large volumeflow of the reactor mixture was withdrawn from the reactor to keep thefill-volume in the reactor constant. The fill-volume in the reactor andthe supplied/discharged volume flows resulted in an average hydrodynamicresidence time of 4.0 hours in the reactor.

Once a steady-state had been achieved, samples of the reactor contentswere withdrawn and a yield of 95-96% for the reaction of ACA to affordACM was determined.

Comparative Example 1 n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate(ACM)

A temperature-controllable, cylindrical glass reactor was filled with aportion of the required MPE to adequately cover the stirring means andthe reactor contents were brought to reaction temperature (typically 85°C.). In the experiments with a pumped circulation system/circulationloop, the circulation loop including the associated pump was also filledwith MPE. Commixing of the reactor contents was accomplished via asix-blade disc stirrer in combination with four baffles. The reactorcontents were always blanketed with nitrogen and the reactor wasoperated without application of superatmospheric pressure.

To ensure reliable starting of the reaction (i.e. reliable initiation),5 minutes before commencement of the metering of the reactants into thereactor a small amount of initiator (0.9-1.0 mL, corresponding to about0.8-0.9 g) was injected into the initially charged MPE previously heatedto reaction temperature (and possibly also circulating through thecirculation loop). The time interval of 5 minutes correspondsapproximately to the half-life of the free-radical initiator tert-butylperneodecanoate at 85° C. Toward the end of the metering time of 4 hours(i.e. more than 40 half-lives of the employed free-radical initiator)the initially injected amount of tert-butyl perneodecanoate had fallento <10⁻¹² parts of the starting amount and thus had no appreciablefurther relevance for any subsequent experiments (for example the ACMproduction in the continuous mode of operation).

Comparative Example 1a Discontinuous Mode of Operation

248.9 g of MPE (98% purity) were initially charged and heated to 85° C.and 0.9 mL (about 0.8 g) of the free-radical-initiator tert-butylperneodecanoate (98% purity) were added. 5 minutes after addition of thefree-radical-initiator tert-butyl perneodecanoate to the MPE wascomplete a mixture of 57.9 g of ACA (99% purity) and 3.0 g of thefree-radical initiator tert-butyl perneodecanoate (98% purity) weremetered into the reactor over a period of 4.0 hours. The concentrationof the free-radical initiator was accordingly 1.0 wt % based on theoverall mixture present in the reactor.

The employed ACA had reacted completely.

Comparative Example 1b Continuous Mode of Operation

The reactor was initially charged with a mixture produced by thediscontinuous mode of operation according to hereinabove-reportedcomparative example 1a. At a reaction temperature of 85° C., the meteredstreams (D1) and (D2) were then simultaneously and separately meteredinto the reactor.

At 85° C., metered stream (D1), MPE, was added to the reactor at 63 mL/hand metered stream (D2), a mixture of ACA and free-radical initiatortert-butyl perneodecanoate, was added to the reactor at 15 mL/h,

the content of the free-radical initiator in the ACA (5.0 wt %) beingchosen such that a content of 1.0 wt % of free-radical initiator in theoverall mixture in the reactor was achieved.

Corresponding to the supplied volume flows, an adequately large volumeflow of the reactor mixture was withdrawn from the reactor to keep thefill-volume in the reactor constant. The fill-volume in the reactor andthe supplied/discharged volume flows resulted in an average hydrodynamicresidence time of 4.0 hours in the reactor.

Once a steady-state had been achieved, samples of the reactor contentswere withdrawn and a yield of 93-94% for the reaction of ACA to affordACM was determined.

The invention claimed is:
 1. Process for producing a compound of formula(I)

wherein a compound of formula (II)

is reacted in a reactor with a compound of formula (III)

wherein in each case: R¹ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R²represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl, (C₆-C₁₀)-aryl,(C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,(C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R³ and R⁴ eachindependently of one another represent hydrogen, (C₁-C₄)-alkyl, phenylor benzyl, R⁵ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, Xrepresents oxygen or sulphur and n is 0 or 1, in the presence of one ormore free-radical-forming substances of formula (V)

wherein R⁶ independently at each occurrence represents hydrogen or(C₁-C₁₀)-alkyl, R⁷ represents hydrogen or (C₁-C₁₀)-alkyl, and R⁸represents methyl, ethyl, 2,2-dimethylpropyl or phenyl, wherein twoseparate metered streams (D1) and (D2) are metered into the reactor asmixtures and these metered streams (D1) and (D2) have the followingcomposition: metered stream (D1) comprises one or more compounds offormula (II) and one or more free-radical-forming substances of formula(V) and metered stream (D2) comprises one or more compounds of formula(III), one or more compounds of formula (II), and optionally one or morefree-radical-forming substances of formula (V), wherein the reaction iscarried out in continuous fashion, and wherein the metered streams (D1)and (D2) are metered into the reactor predominantly simultaneously. 2.Process according to claim 1, wherein metered stream (D1) comprises oneor more compounds of formula (II) and one or more free-radical-formingsubstances of formula (V), wherein metered stream (D1) comprises 10-100mol % of the entirety of the amount of the free-radical-formingsubstances of formula (V) altogether employed.
 3. Process according toclaim 1, wherein metered stream (D1) comprises 20-100 mol % of theentirety of the amount of the free-radical-forming substances of formula(V) altogether employed in the reaction, optionally 25-100 mol %,optionally 30-100 mol %.
 4. Process according to claim 1, whereinmetered stream (D1) comprises 80-100 wt % of the entirety of the amountof compounds of formula (II) altogether employed in the metered streams(D1) and (D2).
 5. Process according to claim 1, wherein metered stream(D2) comprises 80-100 wt % of the entirety of the amount of compounds offormula (III) altogether employed in the metered streams (D1) and (D2).6. Process according to claim 1, wherein metered stream (D1) comprises40-100 mol % of the entirety of the amount of the free-radical-formingsubstances of formula (V) altogether employed in the metered streams(D1) and (D2) and/or metered stream (D2) comprises 0-60 mol % of theentirety of the amount of the free-radical-forming substances of formula(V) altogether employed in the metered streams (D1) and (D2).
 7. Processaccording to claim 1, wherein the entirety of the compound (II) and thefree-radical-forming substances of formula (V) in the metered stream(D1) is 75 to 100 wt % based on the total weight of the metered stream(D1).
 8. Process according to claim 1, wherein reaction is effected at atemperature in the range from 40° C. to 120° C.
 9. Process according toclaim 1, wherein the molar ratio of the entirety of the employedcompound of formula (II) to the entirety of the employed compound offormula (III) is in the range from 8:1 to 1:1.
 10. Process according toclaim 1, wherein one of the compounds or the compound of formula (II)corresponds to formula (IIa)

wherein R¹ represents R² represents, and one of the compounds or thecompound of formula (III) corresponds to formula (IIIa)


11. Process for producing glufosinate

or glufosinate salt, comprising reacting in a reactor a compound offormula (II)

with a compound of formula (III)

to obtain a compound of formula (Ib)

wherein in each case: R¹ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R²represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl, (C₆-C₁₀)-aryl,(C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,(C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R³ and R⁴ eachindependently of one another represent hydrogen, (C₁-C₄)-alkyl, phenylor benzyl, R⁵ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, orrepresents methyl, X represents oxygen or sulphur and n is 0 or 1, inthe presence of one or more free-radical-forming substances of formula(V)

wherein R⁶ independently at each occurrence represents hydrogen or(C₁-C₁₀)-alkyl, R⁷ represents hydrogen or (C₁-C₁₀)-alkyl, and R⁸represents methyl, ethyl, 2,2-dimethylpropyl or phenyl, wherein twoseparate metered streams (D1) and (D2) are metered into the reactor asmixtures and these metered streams (D1) and (D2) have the followingcomposition: metered stream (D1) comprises a mixture of one or morecompounds of formula (II) and one or more free-radical-formingsubstances of formula (V), and metered stream (D2) comprises one or morecompounds of formula (III), one or more compounds of formula (II), andoptionally one or more free-radical-forming substances of formula (V),wherein the reaction is carried out in continuous fashion, and whereinthe metered streams (D1) and (D2) are metered into the reactorpredominantly simultaneously.
 12. Process for producing glufosinateand/or one or more glufosinate salts, optionally glufosinate,glufosinate sodium or glufosinate ammonium, comprising: (a) reacting ina reactor a compound of formula (II)

with a compound of formula (III)

to obtain a compound of either a

or a compound of formula (Ib)

wherein in each case: R¹ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R²represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl, (C₆-C₁₀)-aryl,(C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl, (C₇-C₁₀)-haloaralkyl,(C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, R³ and R⁴ eachindependently of one another represent hydrogen, (C₁-C₄)-alkyl, phenylor benzyl, R⁵ represents (C₁-C₁₂)-alkyl, (C₁-C₁₂)-haloalkyl,(C₆-C₁₀)-aryl, (C₆-C₁₀)-haloaryl, (C₇-C₁₀)-aralkyl,(C₇-C₁₀)-haloaralkyl, (C₄-C₁₀)-cycloalkyl or (C₄-C₁₀)-halocycloalkyl, Xrepresents oxygen or sulphur and n is 0 or 1, in the presence of one ormore free-radical-forming substances of formula (V)

wherein R⁶ independently at each occurrence represents hydrogen or(C₁-C₁₀)-alkyl, R⁷ represents hydrogen or (C₁-C₁₀)-alkyl, and R⁸represents methyl, ethyl, 2,2-dimethylpropyl or phenyl, wherein twoseparate metered streams (D1) and (D2) are metered into the reactor asmixtures and these metered streams (D1) and (D2) have the followingcomposition: metered stream (D1) comprises one or more compounds offormula (II) and one or more free-radical-forming substances of formula(V), and metered stream (D2) comprises one or more compounds of formula(III), one or more compounds of formula (II), and optionally one or morefree-radical-forming substances of formula (V), wherein the reaction iscarried out in continuous fashion, and wherein the metered streams (D1)and (D2) are metered into the reactor Predominantly simultaneously; and(b) using the compound of either formula (I) or formula (Ib) obtained in(a) for producing one or more glufosinate/glufosinate salts, optionallyglufosinate, glufosinate sodium or glufosinate ammonium.
 13. The processaccording to claim 1, wherein metered stream (D1) comprises 40-100 mol %of the entirety of the amount of the free-radical-forming substances offormula (V) altogether employed in the metered streams (D1) and (D2)and/or metered stream (D2) comprises 0-60 mol % of the entirety of theamount of the free-radical-forming substances of formula (V) altogetheremployed in the metered streams (D1) and (D2).
 14. The process accordingto claim 1, wherein the entirety of the compound (II) and thefree-radical-forming substances of formula (V) in the metered stream(D1) is 85 to 100 wt % in each case based on the total weight of themetered stream (D1).
 15. The process according to claim 1, wherein themolar ratio of the entirety of the employed compound of formula (II) tothe entirety of the employed compound of formula (III) is in the rangefrom 5:1 to 2:1.
 16. The process according to claim 1, wherein the oneor more free-radical-forming substances of formula (V) employed in thereaction are selected from the group consisting of tert-butylperoxypivalate, tert-amyl peroxypivalate, tert-butyl peroxyneodecanoate,1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, cumylperoxyneodecanoate, cumyl peroxyneoheptanoate and cumyl peroxypivalate.